The candidate who has risen to the top of the GOP presidential field is now in greater demand, and he insists he is in the race for the long haul. Some voters and analysts remain skeptical.

Reporting from Concord, N.H., and Los Angeles — A day after Herman Cain's first debate appearance as a top-tier contender for the Republican presidential nomination, the former Godfather's Pizza executive strode into the Ninety Nine Restaurant & Pub. The chief hawker of the "9-9-9" tax plan picked up an order of New England fried shrimp for, yes, $9.99, and ran smack into the question uppermost on voters' minds.

"You've piqued a lot of interest," Debbie Mastromarino told Cain as he sauntered over to the bar in his black Stetson hat. "You up for the long haul?"

"Yes ma'am," Cain replied.

"Ya think?" she asked skeptically. "'Cause they all fizzle.… You can't fizzle."

"I won't fizzle," he promised.

With his poll numbers surging and opponents scrambling to stop him, the underfunded and understaffed Cain is no longer just a fringe candidate with a catchy plan for the economy. An NBC/Wall Street Journal poll released late Wednesday had Cain leading the GOP field nationally, with 27% to former Massachusetts Gov. Mitt Romney's 23%.

That puts Cain suddenly in the demanding center of the campaign for president, where questions persist about whether he is the latest rise-and-fall Republican or in the race to stay.

Cain hasn't powered his rise on campaign appearances — he has had few in New Hampshire and Iowa since early summer. He has spent most of October on a book tour to promote his memoir, "This is Herman Cain! My Journey to the White House."

Instead he lifted off on his debate performances and specifically his nonstop touting of the 9-9-9 plan, which would scrap the current federal tax code and replace it with a 9% tax on corporate and personal income and a 9% national sales tax. (He says it would simplify a tax system that Americans abhor. His rivals say it's a simplistic nonstarter that would put his party on record as supporting a new tax.)

The 65-year-old Cain said Wednesday that he had run the campaign "very lean by design."

"We are now going to ramp up. …We now have the money to do so."

His staff said he planned to launch a two-day bus tour Friday that will travel from Memphis to Nashville, across a state that is on no one else's radar. Tennessee's primary is scheduled March 6, weeks after the first states — Iowa, New Hampshire, South Carolina and Nevada — are scheduled to vote. Cain and his aides said the trip was part of a national strategy.

Steve Duprey, a Republican National Committee member from New Hampshire, was doubtful, as were GOP activists in other early states.

"Tennessee? That's not where I'd head right now," Duprey said. "I'd get to New Hampshire and do five town hall meetings a day seven days in a row."

Craig Robinson, founder of the Iowa Republican website, said he had heard that Cain did not plan to visit Iowa until Nov. 19.

"If he came," Robinson said, "he would be a major draw. No one doesn't like Herman Cain." But the fact that Cain is staying away, he said, "makes me question what is he really running for?"

Many believe that Cain, a former radio talk show host and motivational speaker, would like to follow in the footsteps of former Arkansas Gov. Mike Huckabee, who won the party's 2008 Iowa caucuses, then fizzled in the race but landed a fat TV contract for a show on Fox News.

Whatever his goal, Cain's rapid and unexpected ascent in the polls has caused a certain amount of chaos in his organization.

Cain's longtime press secretary left the campaign this month, and her replacement has been struggling to keep up with demands on the candidate's time.

Early Wednesday, reporters who heard that he planned to address New Hampshire legislators wandered the statehouse halls trying to find him. Afterward, Cain chatted with reporters about his book ("It's doing great"), how an Apple computer designed in America with components manufactured in Malaysia and assembled in China would be taxed under his plan ("I have no idea") and how his identity as an African American differs from President Obama's ("I still connect with all people in this country; my church is still in the 'hood").

He also fit in appearances on at least five national television shows.

Some Republicans suggested that Cain's ascent is good news for Romney, who has been considered the front-runner for most of the race, because it puts pressure on other candidates like Texas Gov. Rick Perry. Though Perry has faltered in debate performances, he is a prodigious fundraiser and is still regarded as Romney's most formidable rival.

"This has played out as perfectly as possible for Gov. Romney," said Duprey, who is unaligned in the campaign, though his wife works for Romney's wife.

At the Ninety Nine, Mastromarino, a Republican pharmacy technician, pressed Cain about his 9-9-9 plan, whereupon the candidate gave her his brochure and urged her to "read up" on it.

"I will," she replied. "We'll see if you hang in there."

"If you know me," Cain said, "you know that I'm not going to be the flavor of the week."